Eur. Phys. J. A 17, 235-240 (2003)
DOI: 10.1140/epja/i2002-10158-9

Observation of correlations from collisions

V. Koptev¹, M. Nekipelov^{1, 2}, M. Büscher², S. Dymov^{2, 3}, M. Hartmann², V. Hejny², H.R. Koch², N. Lang⁴, S. Mikirtichyants¹, H. Ohm², A. Petrus³, Z. Rudy^{2, 5}, R. Schleichert², A. Sibirtsev², K. Sistemich², H. Ströher² and K.-H. Watzlawik<sup>2

1</sup>  High Energy Physics Department, Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia
²  Institut für Kernphysik, Forschungszentrum Jülich, D-52425 Jülich, Germany
³  Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region, Russia
⁴  Institut für Kernphysik, Universität Münster, W.-Klemm-Str. 9, D-48149 Münster, Germany
⁵  M. Smoluchowski Institute of Physics, Jagellonian University, Reymonta 4, PL-30059 Cracow, Poland

m.buescher@fz-juelich.de

(Received: 26 November 2002 / Revised version: 24 March 2003 / Published online: 20 May 2003)

Abstract
Results of a first experiment on ( K⁺p) and ( K⁺d) correlations from proton-carbon ( pC) and proton-deuteron ( pd) interactions at beam energies above and much below the threshold for elementary kaon production in nucleon-nucleon reactions ( T_NN=1580 MeV) are discussed. These data, obtained with the ANKE spectrometer at COSY-Jülich, provide first direct evidence for K⁺ production via the two-step mechanism and an indication for a cluster mechanism. It is shown that both processes contribute significantly in pC collisions at 1200 MeV, while they are strongly suppressed at 2300 MeV and also in pd-interactions at 1344 MeV. It is emphasized that the underlying kinematics can be exploited to distinguish between these reaction mechanisms.

PACS
13.60.Le - Meson production.
13.75.Jz - Kaon-baryon interactions.
14.40.Aq - , K, and mesons.
25.10.+s - Nuclear reactions involving few-nucleon systems.

© Società Italiana di Fisica, Springer-Verlag 2003